144 



NA TURE 



\JDec. 1 1, 1884 



SOCIETIES AND ACADEMIES 



London 



Physical Society, November 22. — Prof. Guthrie, President, 

 in the chair. — Mr. James Bewsher was elected a member of the 

 Society. — The following notes were read by Mr. R. T. Glaze- 

 brook, M.A., F.R.S. : — On the permanence of some standards 

 of electrical resistance. The author has had occasion to com- 

 pare with ten standard B.A. units a coil which had been tested 

 by Lord Rayleigh in 1882, the coil then being two years old. 

 He found that its resistance was 9-98335 B.A. units at I4°'05 C, 

 while Lord Rayleigh found the value 9-98330 B.A. units. Thus, 

 either the coil and the standards have changed by exactly the 

 same amount, which is improbable, for they are wires of dif- 

 ferent thickness, or they have all remained permanent. — On the 

 effect of moisture in modifying the refraction of plane-polarised 

 light by glass. The author described some experiments he had 

 been engaged in lately at the Cavendish Laboratory. Plane- 

 polarised light is made to fall on a plate or a wedge of glass at 

 various angles, and the position of the plane of polarisation 

 determined. It is found that this depends greatly on the hygro- 

 metric condition of the air in the neighbourhood of the glass. 

 If moist air be blown on to perfectly clean glass, the plane of 

 polarisation of the emergent light is displaced from its normal 

 position in one direction, while, if dry air be blown, it is dis- 

 placed in the opposite direction. At an angle of incidence of 

 60° the difference between the two positions is from 6' to 8'. If, 

 however, the glass be not perfectly clean, the effect of moisture 

 is at first the same as that of dry air, though on stopping the 

 draught an opposite effect is observed. The author assigns as 

 the cause of this the heating of the surface, which, as Magnus 

 discovered, is produced by a draught of moist air. He finds, 

 on repeating Magnus's experiment, that the heating is not pro- 

 duced if the glass be clean, and he shows by an independent 

 experiment that slight local heating does produce an effect on 

 the plane of polarisation in the same direction as that due to the 

 dry air. — Mr. Glazebrook also exhibited a spectrophotometer 

 described by him in a paper read before the Cambridge Philo- 

 sophical Society (Proc. Phil. Soc. vol. iv. part vi.), and made by 

 the Cambridge Scientific Instrument Company from his design. — 

 A note on a point in the theory of pendent drops, by Mr. A. M. 

 Worthington, was read by the Secretary, Mr. Walter Baily. 

 This was a note upon a paper recently communicated by the 

 author to the Royal Society upon the measurement of the 

 surface-tension of a liquid from the observations of the forms 

 assumed by pendent drops. By making a measurement of a 

 horizontal section of such a drop, and of the angle made by the 

 tangent plane to the surface at the line where the section meets 

 the surface with the horizontal, and knowing the density of the 

 liquid, sufficient data are obtained to determine its surface- 

 tension. Prof. Perry remarking upon this paper gave an 

 account of some researches upon the subject, in which some 

 years since he had assisted Sir William Thomson. On the usually 

 accepted theory of surface-tension based upon the behaviour of 

 liquids in capillary tubes, at every point of the surface of a 

 liquid the equation 



kp 



+ 



must hold where / is the pressure at that point or the differ- 

 ence of pressure on the two sides of the surface, R and R' the 

 two principal radii of curvature, and k a constant. In the case 

 of a drop whose surface is one of revolution about the vertical, 

 the contour may be drawn from the equation. This was done, and 

 theoretical drawings were made of a number of drops. These 

 have since been compared by Sir W. Thomson with enlarged 

 photographs of actual drops, and the results are highly satis- 

 factory. This law no longer holds in the case of a drop at its 

 " critical point," or that point when it is about to fall, since here 

 dynamical action comes in. — Mr. Baily also read a paper by the 

 same author on a new capillary multiplier. This is an appa- 

 ratus for the measurement of surface-tension, and is a modifica- 

 tion of one used by M. Despretz. From one extremity of the 

 arm of a balance is suspended a roll of platinum foil, consist- 

 ing of a strip 50 cm. long and 5 cm. or 6 cm. broad, rolled up, 

 the successive convolutions being prevented from touching by 

 rolling up with the foil a number of small pieces of hard glass 

 tubing about 2 mm. diameter, which occupy the upper part of 

 the helix, and preserve the form of the lower. The coil is 

 cleaned by igniting it in a Bunsen flame, and then suspended 



with its lower end in the liquid to be examined. The increase 

 in weight corrected for the part of the coil immersed is due to 

 the fluid rising between the convolutions. From this the surface- 

 tension is readily calculated. — Mr. Hilger described a new 

 solar eye-piece. In Prof. Pickering's eye-piece there are two 

 rectangular prisms of glass of slightly different refractive 

 indices. The light of the sun undergoes partial reflection at the 

 surface separating the two prisms, the ratio of the reflected to the 

 incident light diminishing with the difference between the re- 

 fractive indices. It is found, however, that such a prism under 

 a high power always gives a double image, due to the two glass 

 surfaces, it being practically impossible, even under enormous 

 pressure, to bring them into true contact. To obviate this Mr. 

 Hilger makes the second prism of Canada balsam, which gives 

 the most satisfactory results, the image being pure and single. 



Vienna 

 Imperial Academy of Sciences, November 6. — On 

 the fossil flora of the breccia of Hoetting, by C. von 

 Ettingshausen. — On resorcin-blue, by P. Weselsky and R. 

 Benedikt. — Carcinological notes, by K. Kcelbel. — On a re- 

 duced organ in Campanula pcrsicifolia and in other species of 

 Campanula, by E. Heinricher. — A new method of combating 

 Phylloxera, by G. Henshel (sealed packet). — Contribution to 

 the anatomy of the male organs of generation, by E. Finger. — 

 On the bodies formed from hydroquinones by melting soda, by 

 L. von Barth and T. Schreder. — On the temperature of the 

 Austrian Alpine countries (part 1), by E. Hann.— On oxyphos- 

 phinic acids, by W. Fossek. — On the length of the year of 

 Sirius, by Th. von Oppolzer. — On the figure of light-waves in 

 the magnetic field, by E. von Fleischl. — On diluvial man from 

 the caves of Stramberg (Moravia), by T. N. Woldrich. 



CONTENTS page 



Health Laboratories as [the Result of the 'Health 



Exhibition 121 



The Butterflies of Europe. By R. McLachlan, 



F.R.S 122 



Elementary Mathematics 123 



Our Book Shelf:— 



Lovell's "Edible Mollusca of Great Britain and Ire- 

 land" 124 



Brown's " Forestry in the Mining Districts of the 



Ural Mountains in Eastern Russia " 124 



Willkomm's " Pyrenaische Halbinsel " 124 



Letters to the Editor : — 



The Prime Meridian Conference. — Gen. Richard 



Strachey, F.R.S. ; Latimer Clark 125 



The Electric Light for Lighthouses and Ships. — A. 



Ainslie Common 125 



Natural Science in Schools.— Prof. Sydney Young 126 



The Edible Bird's-Nest.— Jos. R. Green 126 



The so-called South Plant of Egyptian Art.— W. T. 



Thiselton Dyer, F.R.S 127 



Earthworms.— Frederick Lewis 127 



Injuries caused by Lightning in Africa. — Dr. von 



Danckelman 127 



The Northernmost Extremity of Europe. — A Nor- 

 wegian 127 



Our Future Clocks and Watches.— B. J. Hopkins . 128 



Singular Optical Phenomenon. — X 128 



The Aurora Borealis.— Dr. Sophus Tromholt . . 12S 

 The United States Fish Commission. By Ralph 



S. Tarr , • • • • 128 



The Institution of Engineers and Shipbuilders in 



Scotland '3° 



The Eggs of Monotremes. ByW. Baldwin Spencer. 



(Illustrated) '3 2 



Notes ! 35 



Our Astronomical Column : — 



Wolf's Comet '37 



The Washburn Observatory, Wisconsin 137 



Geographical Notes '37 



Scientific Aspects and Issues of the International 



Health Exhibition. By Ernest Hart 138 



University and Educational Intelligence 143 



Societies and Academies '44 



